MapLayers S3 Class

A lightweight S3 class to manage and draw map layers (ocean, land, coastlines, grid lines, country borders, and an optional center meridian) on an existing plot. Supports "Europe" and "Pacific" map centers. When centered on "Pacific", layers are split into -180 and +180 halves to handle wrapping.

Usage

new_MapLayers(
  Maps,
  terrestrial,
  centerMap,
  showBorders = TRUE,
  grid = FALSE,
  centerLine = FALSE,
  xlim = NULL,
  ylim = NULL
)

Arguments

Maps

A named list of sf spatial objects containing map layers.

terrestrial

Integer; show only estimates on land masses (1), oceans (-1) or all (0); 1 to draw ocean fill, -1 to draw land fill.

centerMap

Character; either "Europe" or "Pacific" (or any non-"Europe" string to trigger split logic).

showBorders

Logical; add country borders.

grid

Logical; add graticule grid lines.

centerLine

Logical; add a vertical line at the center longitude (0 in the plotting coordinate space you provide).

xlim, ylim

Numeric length-2 vectors with plot limits in degrees.

Value

An object of class "MapLayers".

Expected Maps structure

For centerMap == "Europe":

• $ocean, $land, $coast, $grids, $borders

For centerMap != "Europe" (e.g. "Pacific"):

• $`ocean-180`, $`ocean+180`, $`land-180`, $`land+180`

• $`coast-180`, $`coast+180`, $`grids-180`, $`grids+180`

• $`borders-180`, $`borders+180`

All layers are expected as sf objects (polygons/lines). Internally we convert to sp for plotting.

Examples

if (FALSE) { # \dontrun{
ml <- new_MapLayers(Maps, terrestrial = 1, centerMap = "Pacific",
                    showBorders = TRUE, grid = TRUE, centerLine = FALSE,
                    xlim = c(-180, 180), ylim = c(-60, 75))
plot(0, 0, type = "n", xlim = c(-180, 180), ylim = c(-90, 90), xlab = "lon", ylab = "lat")
plot(ml)  # draws ocean, coastlines, optional grid/borders
} # }